Created attachment 302930 [details] testcase When the script sets scrollLeft or scrollTop on a scrollable element (without scrollbars, in this case), we don't get a DOM event for the scroll. Steps to reproduce: Load the testcase and wait one second.
Created attachment 302934 [details] testcase, take 2 fixing testcase (removing irrelevant stuff)
Created attachment 302935 [details] testcase, take 3 really fixing the testcase
WFM on trunk. Fixed by bug 234455, IIRC